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Cahyo AN, Murti RH, Putra ETS, Nuringtyas TR, Fabre D, Montoro P. 2021. Assessment of factual measurement times for chlorophyll-a fluorescence in rubber (Hevea brasiliensis) clones. Biodiversitas 22: 3470-3477. Chlorophyll-a fluorescence is widely used to determine the stress tolerance levels of some plant species. Measurement of chlorophyll-a fluorescence is accurate if the duration of dark adaptation is well defined and optimal Fv/Fm (maximum quantum yield of primary photochemistry/photosynthesis) is achieved. Leaf clips are usually used to darken the leaf prior to measurement. This procedure takes time and limits the use of chlorophyll-a fluorescence parameter in high-throughput screening of genetic populations. This study aimed to determine the most suitable time for the chlorophyll-a fluorescence measurement. This study was carried out on several rubbers (Hevea brasiliensis Müll. Arg.) clones and consisted of two steps. The first step was conducting the measurements at five different times at night: at 7.30, 8.00, 8.30, 9.00, and 9.30 p.m. The second step was conducting the measurements at daytime, which consisted of two factors. The first factor was the measurement time, which was divided into two categories: 7.30 a.m. and 1.30 p.m. The second factor was the duration of dark adaptation using leaf clips, which consisted of nine levels: 0, 15, 30, 45, 60, 75, 90, 105, and 120 min. Additional treatment (measurement at 9.00 p.m. without using leaf clips to darken the leaf) was used as a control. This study revealed that a dark adaptation time of two hours after the sunset was long enough for the rubber leaves chlorophyll-a fluorescence transient to be measured without using leaf clips for the dark adaptation. If the measurement is conducted by 7.30 a.m., the clone RRIM 600, GT1, and SP 217 required 15 min of dark adaptation, whereas clone PB 260 required 60 min of dark adaptation. Furthermore, measurement of chlorophyll-a fluorescence in the afternoon is not recommended due to the potentially high microclimate fluctuation.

This study investigated the effects of salicylic acid (SA) foliar application on Fritillariaprzewalskii under drought stress condition. Plants were subjected to three irrigation regimes, 75-80% control (CK), 60-65% medium stress (M) and 40-45% severe stress (S) of the field capacity and three levels of SA, 0.0, 0.5 and 1.0 mM. Relative water content (RWC), proline content, total soluble carbohydrates, chlorophyll “a” (Chl a), chlorophyll “b” (Chl b), chlorophyll “a + b” (Chl a + b), carotenoids contents, malondialdehyde (MDA) contents and activities of several antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione reductase (GR) and ascorbate peroxidase (APX) activity were measured. RWC, soluble carbohydrates, Chl b, Chl a + b, MDA content and activities of antioxidant enzymes (SOD, POD, CAT, GR and APX) were significantly affected by water deprivation without SA. Exogenous SA significantly increased the content of RWC, total leaf soluble carbohydrates, leaf proline and Chl b at moderate water deficit and severe water deficit. MDA content was decreased significantly by exogenous SA. The activities of antioxidant enzymes (SOD, POD, CAT, GR and APX) were also significantly affected by exogenous SA. However, the content of Chl a, Chl a + b, and carotenoids were not significantly affected by exogenous SA., Cette étude a examiné les effets de l’application foliaire d’acide salicylique (AS) sur Fritillariaprzewalskii en condition de sécheresse. Les plantes ont été soumises à trois régimes d’irrigation : 75-80 % comme contrôle (CK), 60-65 % de stress moyen (M) et 40-45 % de stress sévère (S) de la capacité au champ et trois niveaux d’AS : 0,0, 0,5 et 1,0 mM. Les teneurs en eau relative (RWC), en proline, glucides solubles totaux, chlorophylle « a » (Chl a), chlorophylle « b » (Chl b), chlorophylle « a + b » (Chl a + b), teneurs en caroténoïdes et malondialdéhyde (MDA) ont été mesurées, ainsi que les activités de plusieurs enzymes antioxydantes telles que la superoxyde dismutase (SOD), la peroxydase (POD), la catalase (CAT), la glutathion réductase (GR) et l’ascorbate peroxydase (APX). La RWC, les glucides solubles, Chl b, Chl a + b, la teneur en MDA et les activités des enzymes antioxydantes (SOD, POD, CAT, GR et APX) étaient significativement affectées par la privation en eau sans AS. L’AS exogène a considérablement augmenté la teneur en RWC, en glucides solubles dans les feuilles, en proline et en Chl b en déficit hydrique modéré et sévère. Le contenu en MDA a été réduit de manière significative par l’AS exogène. Les activités des enzymes antioxydantes (SOD, POD, CAT, GR et APX) étaient également significativement affectées par les AS exogènes. Cependant, les teneurs en Chl a, Chl a + b et les caroténoïdes n’étaient pas significativement affectées par les AS exogènes.

International audience; Leaf biochemical and structural traits are vegetation characteristics related to various physiological processes. Taking advantage of the physical relationship between optical properties and leaf biochemistry, field-based spectroscopy has allowed for the rapid estimation of leaf biochemical constituents and repeated non-destructive measurements through time. Leaf constituent retrieval from leaf optical properties following inversion of the physically-based radiative transfer model PROSPECT is now a popular method, but some cases prompt poor retrieval success and this approach requires a strict inversion procedure. We investigated the performances of different inversion procedures for the estimation of leaf constituents, specifically chlorophyll a and b, carotenoids, water (EWT), and dry matter (LMA) from >1400 broadleaf samples, including the definition of optimal spectral subdomains, and the use of leaf reflectance or transmittance alone. We also developed a strategy to obtain prior information on the leaf structure parameter (N) in PROSPECT, when only reflectance or transmittance is measured, and examined the influence of this prior information in combination with different inversion procedures. We found that using the full domain of reflectance or transmittance only systematically leads to suboptimal estimation of chlorophyll a and b, carotenoids, EWT, and LMA, due to either the combined absorption of multiple constituents or inaccurate estimation of the N parameter. Our study confirms that the selection of optimal spectral subdomains leads to improved estimation of all leaf constituents, from 700 to 720 nm for chlorophyll a and b, 520–560 nm for carotenoids, and from 1700 to 2400 nm for EWT and LMA. Prior information on N, computed directly from the spectra, leads to systematic improved estimation of leaf constituents when only reflectance or transmittance is measured, with reductions in normalized root mean square error from 8 to 37%. We strongly recommend using optimal subdomains when inverting PROSPECT to retrieve leaf constituents, and with the availability of only reflectance or transmittance we further recommend the use of prior information on the N parameter.

International audience; An underwater volcanic eruption off the Vava'u island group in Tonga on 7 August 2019 resulted in the creation of floating pumice on the ocean's surface extending over an area of 150 km2. The pumice's far-reaching effects from its origin in the Tonga region to Fiji and the methods of automatic detection using satellite imagery are described, making it possible to track the westward drift of the pumice raft over 43 days. Level 2 Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIRS), Sentinel-3 Ocean and Land Color Instrument (OLCI), and Sentinel-3 Sea and Land Surface Temperature Radiometer (SLSTR) imagery of sea surface temperature, chlorophyll-a concentration, quasi-surface (i.e., Rayleigh-corrected) reflectance,and remote sensing reflectance were used to distinguish consolidated and fragmented rafts as well as discolored and mesotrophic waters. The rafts were detected by a 1 to 3.5°C enhancement in the MODIS-derived "sea surface temperature" due to the emissivity difference of the raft material. Large plumes of discolored waters, characterized by higher satellite reflectance/backscattering of particles in the blue than surrounding waters (and corresponding to either submersed pumice or associated white minerals), were associated with the rafts. The discolored waters had relatively lower chlorophyll-a concentration, but this was artificial, resulting from the higher blue/red reflectance ratio caused by the reflective pumice particles. Mesotrophic waters were scarce in the region of the pumice rafts, presumably due to the absence of phytoplanktonic response to a silicium-rich pumice environment in these tropical oligotrophic environments. As beach accumulations around Pacific islands surrounded by coral shoals are a recurrent phenomenon that finds its origin far east in the ocean along the Tongan trench, monitoring the events from space, as demonstrated for the 7 August 2019 eruption, might help mitigate their potential economic impacts.

Multispectral and hyperspectral sensor data of the bio-optical parameters with a high spatial resolution are important for monitoring and mapping of the coastal ecosystems and estuarine areas, such as the Kneiss Islands in the Gulf of Gabes. Sentinel 2 S2A and Hyperion Earth observing-1 (EO1) imaging sensors reflectance data have been used for water quality determination and mapping of turbidity TU and chlorophyll Chl-a in shallow waters. First, we applied a tidal swing area mask based on uncorrelated pixel via 2D scatter plot between 665 nm and 865 nm to eliminate the overestimation of the concentration of water quality parameters due to the effect of the bottom reflection. The processing for mapping and validating Chl-a, Turbidity S2A, and EO1 were performed using a relation between reflectance bands and in situ measurements. Therefore, we were able to validate the performance of the case 2 regional coast colour processor (C2RCC) as well as our region-adapted empirical optical remote sensing algorithms. Turbidity was mapped based on the reflectance of 550 nm band for EO1 (R² = 0.63) and 665 nm band for S2A (R² = 0.70). Chlorophyll was mapped based on (457/528 nm) reflectance ratio (R² = 0.57) for EO1 and (705/665 nm) reflectance ratio (R² = 0.72) for the S2A.

Measurement of chlorophyll content using destructive methods is not efficient due to a large number of samples, cost, and time needed. Estimationof chlorophyll content by nondestructive methods using handheld chlorophyll meter may be considered to improve efficiency. This research aimed to determine the formula to convert SPAD-502 and atLEAF CHL PLUS values (relative indicator of chlorophyll content) to estimated (absolute) rubber leaves chlorophyll content. Twenty leaves of rubber plant were measured using SPAD-502 and atLEAF CHL PLUS at the same time to determine SPAD-502 and atLEAF CHL PLUS values. The measured leaves were then collected to determine the chlorophyll content using a standard laboratory procedure. Regression and correlation analyses (among 3 methods) were conducted using SAS v.9 software. The results showed that between SPAD-502 and atLEAF CHL PLUS values were closely correlated, hence both of the devices can substitute each other to estimate rubber leaf chlorophyll content. In addition, the relationship between atLEAF CHL PLUS and SPAD-502 values with actual chlorophyll content of rubber clone SP 217, PB 260, GT1, and all clones (general) were significant with high coefficient of determination (R2) as well as low Root Mean Square Error (RMSE) and Coefficient of Variation (CV). Therefore, by using formula determined in this study, both atLEAF CHL PLUS and SPAD-502 can be suggested for accurate, fast, and non-destructive estimation of chlorophyll content of rubber plant leaf.

The Centre Vinicole-Champagne Nicolas Feuillatte would like to set up wine repositores to know the quality from the vine until when the must arrived in its place. It is important to underlinethe fact that it doesn’t own any vine. That’s why the studies have to be done with adherents. The aim of this subject is to determine repositories to get the best aromatic potential for white wines and also the best anthocyanin potential for the color of red wine. We will put the light on Montgueux with its Chadronnay which are well known for exotic fruits flavors. All theses potentials cans be reached if the vine is in a good physiological condition with water and nitrogen. To do this project, we choose to study the vine status, the berry loading and the sensory analysis of wine. We hypothesize that depending of the berry load the day of harvest is an relevent indicator to get the aromatic and wished profile. After having selected the study sites and having met the winegrowers, we measured the nitrogen with the chlorophyll rate which is the leaves and the presence of stress or not with the level of flavonols. We did the measurement twice : first at the blooming when the vine no longer used its reserves but we have photosynthesis to develop, and for the closing of bunches to know the conditions of the vine before maturation grape . We tracked the effects of climate impacts with rainfall and water balance through CIVC stations. For the red wine sites, we haven’t been able to measure anthocyanin chemically, we had only a tool to measure a potential but we don’t know its relevance. The following of Montgueux Chardonnay has shown a fast and ongoing sugar loading in berries and no matter the date of harvest we get one parcel with exotic flavors and an other parcel no exotic flavors. In the future we should study the lead role of nitrogen and water and the date of harvest depending on sugar loading berries.; Le Centre Vinicole-Champagne Nicolas Feuillatte souhaite mettre en place des référentiels viticole pour avoir un suivi qualitatif de la vigne jusqu’à sa cuverie. Il est important de noter que cette structure est une union de coopérative qui ne possède pas de vignes. Les référentiels et les études sont à mener avec les adhérents. L’objectif est de déterminer un référentiel pour les raisins en ayant atteint l’optimum de leur potentiel aromatique et pour les sites de vinification rouge et rosé un potentiel d’anthocyanes à maturité phénolique. Plus précisément, le profil aromatique de fruits exotiques sur les Chardonnay de Montgueux a été l’objet d’une partie de cette étude. Ces potentiels ne peuvent être obtenus seulement si la vigne est en bon état physiologique avec une alimentation en azote et eau. Pour répondre à cette problématique, nous avons choisi de nous baser sur le suivi végétatif de la vigne, le chargement en sucre par baie lors du suivi maturité et l’analyse sensorielle des vins clairs. Nous avons émis l’hypothèse qu’en fonction du chargement en sucre la date de récolte est un indicateur clé pour obtenir le profil aromatique souhaité. Après avoir sélectionné les sites d’études et rencontré les viticulteurs, nous avons mesuré l’état azoté à travers le teneur en chlorophylle des feuilles et la présence d’une contrainte ou non à travers le taux de flavonols. Cette mesure a été effectué deux fois : à la floraison, qui est la période où la vigne n’utilise plus ses réserves mais la photosynthèse pour se développer, et à la fermeture de grappes pour connaître les conditions de la vigne avant la maturation du raisin. Nous avons suivi les indicateurs climatiques avec la pluviométrie et le bilan hydrique grâce aux stations du CIVC. Nous avions un outil pour mesurer le potentiel anthocyanes pour les sites à vin rouge cependant faute d’organisation nous avons pu aboutir à l’étude complète de cette partie du projet. Le suivi des Chardonnay de Montgueux a montré un chargement en sucre continu et rapide avec un profil thiolé pour une parcelle et un profil sans fruit exotique pour une autre, et ce résultat sur 3 dates de récoltes différentes. En perspectives il s’agirait d’étudier le rôle de l’eau et de l’azote sur les prochains millésimes et la date de récolte en fonction des cinétiques de chargement en sucre par baie.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE [Axe_IRSTEA]TETIS-ATTOS; International audience; Finding suitable models of canopy reflectance in forward simulation mode is a prerequisite for their use in inverse mode to characterize canopy variables of interest, such as leaf area index (LAI) or chlorophyll content. In this study, the accuracy of the three-dimensional reflectance model DART (Discrete Anisotropic Radiative Transfer) was assessed for canopies of different genotypes of Eucalyptus, having distinct biophysical and biochemical characteristics, to improve the knowledge on how these characteristics are influencing the reflectance signal as measured by passive orbital sensors. The first step was to test the model suitability to simulate reflectance images in the visible and near infrared. We parameterized DART model using extensive measurements from Eucalyptus plantations including 16 contrasted genotypes. Forest inventories were conducted and leaf, bark, and forest floor optical properties were measured. Simulation accuracy was evaluated by comparing the mean top of canopy (TOC) bidirectional reflectance of DART with TOC reflectance extracted from a Pleiades very high resolution satellite image. Results showed a good performance of DART with mean reflectance absolute error lower than 2%. Intergenotype reflectance variability was correctly simulated, but the model did not succeed at catching the slight spatial variation for a given genotype, excepted when large gaps appeared due to tree mortality. The second step consisted of sensitivity analysis to explore which biochemical or biophysical characteristics influenced more the canopy reflectance between genotypes. Perspectives for using DART model in inversion mode in these ecosystems were discussed. [ABSTRACT FROM PUBLISHER]

International audience; The objective of this study was to evaluate the effect of banana phenological stages on the chlorophyll content of its leaves in order to assess possible restrictions on the potential use of remote sensing for nutritional diagnoses when phenological stages cannot be discriminated on images. Chlorophyll measurements were made with a Dualex sensor at different positions on banana leaves with different ranks on the plant, on plants at different phenological stages and located in different fields of a commercial farm. The effect of these factors was studied using mixed models with nested factors and the results showed that they have a significant effect on the chlorophyll content. It is therefore suggested to take into account the diversity of phenological stages in banana fields before considering nutritional diagnoses services based on remote sensing.

Arabica coffee is a main economic crop throughout Central and South American highlands, where millions of people get primary outcome. Last coffee leaf rust (CLR) epidemic event in 2011, which impacted 53% of the coffee region areas, provoking losses up to USD 500 million, remembered the high vulnerability of the coffee sector to the fungus Hemileia vastatrix, causal agent of this disease and considered as the main restrictive illness for all coffee regions around the world. The main problem remains that the current commercial varieties reputed as "resistant", become sensitive to the CLR. During the last twenty years, coffee geneticist have created several intra-specific hybrids between commercial varieties and wild coffee accessions. Field observations confirmed that coffee hybrids are more productive and less impacted by the CLR even in regions where resistant materials become susceptible. Such field observations are in agreement with the general idea that hybrid plants present high homeostasis in terms of growth, yield and disease resistance. The aim of this research was to investigate the physiological response of coffee hybrids before and after inoculation with the CLR. Using controlled conditions, the metabolic response and physiological status of two hybrid genotypes were assessed under different stressful conditions involving three limiting factors: temperature, luminosity and nitrogen input. Hybrid behavior was compared to an inbred line tested under similar conditions. Results demonstrated that whatever the agronomic conditions and the temperature regimes, hybrids under test were less sensitive to CLR than the inbred line. Interestingly, the detailed transcriptomic analysis revealed that coffee hybrids seem to exhibit an altered circadian clock resulting in a higher photosynthetic efficiency together with an increased concentration of chlorophyll. Most of the over-expressed genes identified in the hybrids after CLR inoculation were associated to basal resistance mechanisms, while genes identified in the inbred line, were more related to abiotic stress responses. Overall our findings suggest that under stressful conditions, coffee hybrids are able to rapidly modify their energetic metabolism machinery leading to a more effective and rapid response to rust attack compared to the inbred line.

Oceanographic in situ data collected in the Gulf of Guinea during six cruises carried out between 2005 and 2007 were analysed to study the influence of equatorial upwelling on the productivity of the region. At 10°W, observations during boreal summer and autumn cruises captured seasonal upwelling influences. In response to the shoaling pycnocline in June 2005, higher concentrations of nitrate and chlorophyll fluorescence were recorded at the ocean surface in June than in September. Our findings challenge the paradigm that westward advection from the nutrient-rich African coast is responsible for equatorial enrichment in the Gulf of Guinea. Vertical sections of the parameters under study in the summer of 2005 showed no westward advection from 3°E to 10°W within the equatorial band. This emphasizes the important role of vertical processes in equatorial enrichment at 10°W. An additional aspect of our study provides evidence of the impact on nutrient and chlorophyll distribution of off-equatorial westward recirculation of equatorial undercurrent waters (observed between 2°and 3°S). Key words: Advection, equatorial undercurrent, equatorial upwelling, Gulf of Guinea, nutrients, phytoplankton biomass.

Introduction. La gestion optimale de la fertilisation azotée des cultures nécessite l’utilisation de méthodes qui permettent d’évaluer rapidement et avec précision le statut azoté de la biomasse aérienne en cours de saison. C’est le cas des mesures optiques sur le végétal et parmi celles-ci, les approches basées sur la mesure de la fluorescence chlorophyllienne (ChlF) des feuilles occupent une place intéressante. Les potentialités de la ChlF sont étudiées depuis plusieurs années pour détecter et quantifier différents stress biotiques et abiotiques des plantes et la ChlF peut s’envisager pour l’évaluation du statut azoté. Ces approches permettent a priori de pallier certaines limitations des méthodes souvent utilisées pour l’évaluation du statut azoté basées sur la transmission ou la réflexion de la lumière et reliées à la teneur en chlorophylle des feuilles. Littérature. Dans cette revue, deux approches basées sur la ChlF sont examinées. La première étudie la ChlF variable, ou cinétique de Kautsky, qui représente l’approche classiquement abordée par la majorité des auteurs. La seconde approche repose sur l’estimation par la ChlF de la concentration en composés foliaires métabolites de la plante, plus spécifiquement la chlorophylle et les composés phénoliques (en particulier les flavonoïdes). Pour chaque approche, les caractéristiques de la ChlF sont examinées, expliquant leurs liens et leurs applications dans l’évaluation du statut azoté des cultures. Conclusions. Parmi les deux approches analysées, l’utilisation du rapport de ChlF qui combine l’estimation de la concentration en chlorophylle et en flavonoïdes au niveau de la feuille apparait comme une approche potentiellement pertinente pour évaluer le statut azoté des cultures, ces deux concentrations étant en relation étroite avec la teneur en azote des feuilles., Use of chlorophyll fluorescence for the evaluation of crops nitrogen status. A reviewIntroduction. Optimizing the nitrogen (N) fertilization of crops requires the use of methods that quickly and accurately assess the N status of aboveground biomass during the growing season. Optical measurements on plants allow the achievement of this goal and, among these approaches, the leaf chlorophyll fluorescence based method (ChlF) appears promising. The potential of ChlF has been studied for many years. The value of this method for detecting and quantifying various biotic and abiotic plant stresses has been assessed as well as its potential for the evaluation of crop N status (CNS). For this last application, ChlF could offer solutions to the limitations of the usual methods for evaluating CNS, which are based on light transmittance or reflectance and are related to leaf chlorophyll content. Literature. In this report, two ChlF based approaches are reviewed. The first approach is variable ChlF, or Kautsky kinetics, which represents the approach taken in the majority of the published work examined in the field of ChlF. The second approach is based on ChlF sensing methods for the estimation of the concentration of leaf metabolite compounds in plants, particularly that of leaf chlorophyll and phenolic compounds (mainly flavonoids). The characteristics and the applications of these two fluorescence approaches are studied for their potential use for the in-season monitoring of CNS.Conclusions. Of these two approaches, the use of the ratio of fluorescence combining the estimation of concentrations of leaf chlorophyll and flavonoid content appears to be a relevant potential method to assess CNS, as both concentrations are in close relationship with leaf N concentration.

The detection of plant diseases, including fungi, is a major challenge for reducing yield gaps of crops across the world. We explored the potential of the PROCOSINE radiative transfer model to assess the effect of the fungus Pseudocercospora fijiensis on leaf tissues using laboratory-acquired submillimetre-scale hyperspectral images in the visible and near-infrared spectral range. The objectives were (i) to assess the dynamics of leaf biochemical and biophysical parameters estimated using PROCOSINE inversion as a function of the disease stages, and (ii) to discriminate the disease stages by using a Linear Discriminant Analysis model built from the inversion results. The inversion results show that most of the parameter dynamics are consistent with expectations: for example, the chlorophyll content progressively decreased as the disease spreads, and the brown pigments content increased. An overall accuracy of 78.7% was obtained for the discrimination of the six disease stages, with errors mainly occurring between asymptomatic samples and first visible disease stages. PROCOSINE inversion provides relevant ecophysiological information to better understand how P. fijiensis affects the leaf at each disease stage. More particularly, the results suggest that monitoring anthocyanins may be critical for the early detection of this disease.

Iron-Sulfur ([Fe-S]) clusters are metal cofactors of proteins involved in many fundamental metabolic pathways and cellular processes occurring in both prokaryotes and eukaryotes ( e.g. respiration, photosynthesis). [Fe-S] clusters participate in electrontransfer, substrate binding/activation, iron and sulfur storage, regulation of gene expression, and enzyme activity. The [Fe-S] cluster biogenesis machinery is composed of scaffold proteins that build the cluster de novo and of carrier proteins that transfer the [Fe-S] prosthetic groups to their target proteins (also called apoproteins). In plants three different machineries lead to [Fe-S] cluster assembly, namely the mitochondrial ISC (Iron Sulfer Cluster) system, the chloroplastic SUF (SUlFur mobilization) system and the cytosolic CIA (Cytosolic Iron-sulfur cluster Assembly) system. Our team focuses mainly on the chloroplastic SUF system and specifically on the characterization of a [Fe-S] carrier proteins named NFU2 ( NiFU-LIKE PROTEIN 2) and its potential role on the maturation of the 45 putative chloroplastic [Fe-S] cluster proteins. The [Fe-S] cluster acquisition of only 5 targets among the 45 putative chloroplastic [Fe-S] cluster proteins has already been explored. Thus, the identification of the carriers that act on the other 40 targets is still a big challenge. In order to shed new light on this process, we have initiated the global characterisation of the nfu2 mutant using proteomic (quantitative label free mass-spectrometry strategy) and metabolomic approaches. Results obtained within the frame of this work will be discussed.

International audience; Remote sensing has gained much attention for agronomic applications such as crop management or yield estimation. Crop phenotyping under field conditions has recently become another important application that requires specific needs: the considered remote-sensing method must be (1) as accurate as possible so that slight differences in phenotype can be detected and related to genotype, and (2) robust so that thousands of cultivars potentially quite different in terms of plant architecture can be characterized with a similar accuracy over different years and soil and weather conditions. In this study, the potential of nadir and off-nadir ground-based spectro-radiometric measurements to remotely sense five plant traits relevant for field phenotyping, namely, the leaf area index (LAI), leaf chlorophyll and nitrogen contents, and canopy chlorophyll and nitrogen contents, was evaluated over fourteen sugar beet (Beta vulgaris L.) cultivars, two years and three study sites. Among the diversity of existing remote-sensing methods, two popular approaches based on various selected Vegetation Indices (VI) and PROSAIL inversion were compared, especially in the perspective of using them for phenotyping applications. Overall, both approaches are promising to remotely estimate LAI and canopy chlorophyll content (RMSE'10%). In addition, VIs show a great potential to retrieve canopy nitrogen content (RMSE=10%). On the other hand, the estimation of leaf-level quantities is less accurate, the best accuracy being obtained for leaf chlorophyll content estimation based on VIs (RMSE=17%). As expected when observing the relationship between leaf chlorophyll and nitrogen contents, poor correlations are found between VIs and mass-based or area-based leaf nitrogen content. Importantly, the estimation accuracy is strongly dependent on sun-sensor geometry, the structural and biochemical plant traits being generally better estimated based on nadir and off-nadir observations, respectively. Ultimately, a preliminary comparison tends to indicate that, providing that enough samples are included in the calibration set, (1) VIs provide slightly more accurate performances than PROSAIL inversion, (2) VIs and PROSAIL inversion do not show significant differences in robustness across the different cultivars and years. Even if more data are still necessary to draw definitive conclusions, the results obtained with VIs are promising in the perspective of high-throughput phenotyping using UAV-embedded multispectral cameras, with which only a few wavebands are available.

Thermal stress affects organism performance differently depending on the ambient temperature to which they are acclimatized, which varies along latitudinal gradients. This study investigated whether differences in physiological responses to temperature are consistent with regional differences in temperature regimes for the stony coral Oculina patagonica. To resolve this question we experimentally assessed how colonies originating from four different locations characterized by >3°C variation in mean maximum annual temperature responded to warming from 20 to 32°C. We assessed plasticity in symbiont identity, density, and photosynthetic properties, together with changes in host tissue biomass. Results show that, without changes in the type of symbiont hosted by coral colonies, O. patagonica has limited capacity to acclimatize to future warming. We found little evidence of variation in overall thermal tolerance, or in thermal optima, in response to spatial variation in ambient temperature. Given that the invader O. patagonica is a relatively new member of the Mediterranean coral fauna our results also suggest that coral populations may need to remain isolated for a long period of time for thermal adaptation to potentially take place. Our study indicates that for O. patagonica, mortality associated with thermal stress manifests primarily through tissue breakdown under moderate but prolonged warming (which does not impair symbiont photosynthesis and, therefore, does not lead to bleaching). Consequently, projected global warming is likely to causes repeat incidents of partial and whole colony mortality and might drive a gradual range contraction of Mediterranean corals. This study was partially funded by the Journal of Experimental Biology Travelling fellowship (RR-M), by the Centre Scientifique de Monaco, and James Cook University (MH). The work contributes to the EU project: ‘Mediterranean Sea Acidification under a changing climate’ (MedSeA; grant agreement 265103).

On the extremely turbid waters of French Guyana, the high-resolution satellite imagery (300 m) seems a very good tool for monitoring coastal and estuarine waters. It is possible to adjust the algorithms and calculation methods to be in the range of values suggested by in-situ measurements and thus, have the long data series, where P90chla and P90turbi parameters can be calculated on the MEC., Sur les eaux extrêmement turbides de Guyane, l’imagerie satellitaire à haute résolution (300 m) semble un très bon outil de suivi des masses d’eau côtières et même estuariennes. Il est possible d’ajuster les algorithmes et méthodes de calcul pour se trouver dans la gamme de valeurs suggérées par les mesures in-situ disponibles et ainsi disposer de longues séries de données, où les paramètres P90chla et P90turbi peuvent être calculés sur la MEC.

The Indian Ocean Dipole (IOD) and the El Niño/Southern Oscillation (ENSO) are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. A negative influence of IOD on chlorophyll concentrations is shown in a region around the southern tip of India in fall. IOD also depresses depth-integrated chlorophyll in the 5–10° S thermocline ridge region, yet the signal is negligible in surface chlorophyll. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Yet unlike most other regions examined, the combined explanatory power of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is relatively low in this region, suggestive that other drivers are important there. We show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. Our results suggest that ENSO and IOD cause significant and predictable regional re-organisation of chlorophyll via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon budgets.

Methods are presented testing the suitability of PROSAIL radiative transfer model for analysing HyMap imaging spectroscopy data over grassland. The presented methods include forward modelling and cross-checks of 2D correlation plots. In the forward modelling, it is taken into account that the in situ data are not error free. To increase the predictive power of PROSAIL, a simple and fully automatic feature selection (FS) algorithm is presented identifying and discarding poorly modelled wavebands, yielding more reliable parameter retrievals.

formes alternatives ou complementaires a la production primaire planctonique. Du fait de la faible profondeur des reservoirs, le sediment peut constituer un support favorable au developpement d’algues benthiques actives si elles sont suffisamment eclairees. D’importants peuplements de macrophytes peuvent par ailleurs coloniser la peripherie des retenues, tandis que la presence en grand nombre de supports divers (arbres ennoyes, macrophytes) est susceptible de favoriser le developpement du periphyton.

Clidemia hirta L., a tropical shrub used for traditional medicine in numerous countries, could constitute a new resource of phytochemicals for cosmetic applications. In vitro micropropagation of C. hirta was used to evaluate the influence of different culture media on plant growth, production of phytochemicals, and the antioxidant and antibacterial properties of leaf extracts. Quoirin and Lepoivre medium and Lloyd and McCown's woody plant medium gave the best results. Both production of phytochemicals (i.e., flavonoids, phenolics and saponins) and biological activities were affected by the culture medium composition with the strongest effects for plants cultivated on Quoirin and Lepoivre medium. Strong correlations were shown between the antibacterial activity and the saponin content and between the antioxidant capacity and the flavonoid content. The present study shows how mineral nutrition influences the production of secondary metabolites in C. hirta, thus modulating the biological activities of extracts with a view to their possible use in the cosmetic industry., Clidemia hirta L., un arbuste tropical utilisé en médecine traditionnelle dans de nombreux pays, pourrait constituer une ressource intéressante pour des applications cosmétiques. La micropropagation de C. hirta in vitro a été utilisée pour évaluer l'influence des milieux de culture sur la croissance des plantes ainsi que le contenu phytochimique et les activités antioxydantes et antibactériennes des extraits de leurs feuilles. Le milieu Quoirin et Lepoivre et le milieu Llyod et Mc Cown donnent les meilleurs résultats. Tant les contenus en flavonoïdes, composés phénoliques et saponines que les activités biologiques sont affectés par la composition du milieu, les meilleures valeurs étant obtenues avec le milieu Quoirin et Lepoivre. Des corrélations fortes sont observées entre activité antibactérienne et contenu en saponines, ainsi qu'entre capacité antioxydante et contenu en flavonoïdes. Cette étude montre l'influence de la nutrition minérale sur la production de métabolites secondaires chez C. hirta et son effet sur les activités des extraits qui peuvent en être dérivés pour une utilisation en cosmétique.

International audience; Frequency and intensity of heat waves and drought events are expected to increase in Europe due to climate change. European beech (Fagus sylvatica L.) is one of the most important native tree species in Europe. Beech populations originating throughout its native range were selected for common-garden experiments with the aim to determine whether there are functional variations in drought stress responses among different populations. One-year old seedlings from four to seven beech populations were grown and drought treated in a greenhouse, replicating the experiment at two contrasting sites, in Italy (Mediterranean mountains) and Germany (Central Europe). Experimental findings indicated that: (1) drought (water stress) mainly affected gas exchange describing a critical threshold of drought response between 30 and 26% SWA for photosynthetic rate and C-i/C-a, respectively; (2) the C-i to C-a ratio increased substantially with severe water stress suggesting a stable instantaneous water use efficiency and an efficient regulation capacity of water balance achieved by a tight stomatal control; (3) there was a different response to water stress among the considered beech populations, differently combining traits, although there was not a well-defined variability in drought tolerance. A combined analysis of functional and structural traits for detecting stress signals in beech seedlings is suggested to assess plant performance under limiting moisture conditions and, consequently, to estimate evolutionary potential of beech under a changing environmental scenario.

We report the development of a new lidar system for airborne remote sensing of chlorophyll fluorescence (Ch1F) and vertical profile of canopies. By combining laser induced fluorescence (LIF), sun-induced fluorescence (SIF) and canopy height distribution, the new instrument will allow the simultaneous assessment of gross primary production (GPP), photosynthesis efficiency and above ground carbon stocks. Technical issues of the lidar development are discussed and expected performances are presented.